We installed 24x24 tiles during our recent kitchen reno. Our house was built in 1923 so nothing was level. Our GC ripped out everything to the sub-floor and the tile-sub leveled the floor with a layer of mud. The mud is 1" thick in some areas and as much as 3" in others. After the mud dried the tiles were installed without incident.
Here's a shot

A section of our kitchen floor was uneven. We installed 18x18 tile and there is lippage. It hasn't bothered me so far. I notice it only when walking the floor on bare feet. Installer inserted wood shims into the mortar to level it out. I don't know if that is the recommended way to do it but it has held up for a year and a half.

What about that self leveling stuff. Isn't that what it's made for?

"QUIKRETE� Fast-Setting Self-Leveling Floor Resurfacer (No. 1249-51) is a self-finishing interior floor topping and underlayment specially formulated to produce smooth surfaces ready for the installation of ceramic tile, resilient flooring or other finishes. No troweling required.
Sets in 3-4 hours"

Here is a link that might be useful: Leveler for concrete floors

We put 8x24 tile on a slab after tearing up 8x8 ceramic tile that had been down FOREVER. We did the demo but had tile installers put down the new tile (about 1200 sq. ft). They just put up the floor where necessary. It's been about 8 months and it's perfect.

That Leveler for concrete floors is probably what was used the first time. The problem is that there is a permanent wall in the middle of one of the lowest spots and the tile goes around the corner there and then butts up against the wood floor.

Wow, 3 inches is a big difference. I bet ours is only 1-1/2 inches at most. But I want it to meet up evenly with the wood floor.

There will be a "Transition" profile strip added to the edge of the tile floor where it butts into the wood floor at a higher level. It's not a big deal. Everyone in the world says that they don't want one, but then they get used to it later and don't even notice it.

"SLC" can level the floor, very well. But, to get results one has to read the instructions printed on the bag, and follow them too. Many installers don't read, or they may read but then not follow instructions well.

Marti- I would look into good quality vinyl flooring. It's much easier on the feet and back...and there are tons of choices. Easy to clean and easy to replace down the road, if you decide you want a different style :)

marti - get a 2nd opinion on what to do about leveling your floor.

also, there are vinyl tiles. 18 x 18 is also available i think. Much easier on the feet. As I've gotten older I consider the comfort of my feet, legs and back over what the trend is. i also consider what is easier to clean.

The tile world is changing right now. Cutting edge tile is produced by ink jet. That means pictures of real stone are shot and tile is printed with up to 58 ink jet heads in high resolution; up to 96 different images in a series not 9 with the conventional roller or silk screen approach. So what does that mean for you. I got 2 cases of Ink jet tile; since all tiles seem different a person can not tell from a single tile. When I laid the 18 by 18 down it didn't quite work. So I tried 6 by 6. Wow it looked like real stones. I want to try a box of 9 by 9 by Panaria. The world of design changes constantly. With ink jet tiles and stain proof grout we may move back to smaller tiles. Everything goes in cycles. Lowe's (my local store; not the one 2 miles down) got two types of ink jet tiles last week by Stone Peak. I am going to use the 6 by 6 to make a countertop for a bathroom. Looks sooo real. Ask around at tile places if they have ink jet tile yet. Most will look at you like your nuts and want you to explain what you mean, but some are up to date. Alway, always look at a whole case before you make a decision; that will give you a hint as to what you will get.

Here is a link that might be useful: See D' mansion and VItalyty

That's interesting bugbite, I'll check it out.

davidro1, we have transition strips now between the tile and the wood and I hate it. Have to lift the vacuum (and everything roller) over it. I consciously have to lengthen or shorten my step so I don't land on it. I really do hate it.